London 'plague pits' yield secrets of how the Black Death evolved from harmless soil bug

DNA experts have sequenced the entire genome of the bubonic plague in a bid to help understand the spread of infectious diseases.

It is first time scientists have been able to reconstruct an ancient pathogen and it will allow researchers to track changes in its evolution and virulence over time.

The work by an international team of researchers from Germany and Canada, published in the journal Nature, could lead to a better understanding of modern infectious diseases.

Breakthrough: Scientists have reconstructed the genome of the black death from the remains of five plague victims found buried beneath East Smithfield in London

In a separate recent study, the team also described a novel approach to pulling out tiny degraded DNA fragments of the causative agent of the Black Death, and showed how a specific variant of the Yersinia pestis bacterium was responsible for the plague that killed 50 million Europeans between 1347 and 1351.

After that success, the next major step was to attempt to 'capture' and sequence the entire genome, said geneticist Hendrick Poinar of the University of Tubingen.

RELATED ARTICLES

Share this article

'The genomic data show that this bacterial strain, or variant, is the ancestor of all modern plagues we have today worldwide, he said.

'Every outbreak across the globe today stems from a descendant of the medieval plague.

Researcher: Geneticist Hendrik Poinar

'With a better understanding of the evolution of this deadly pathogen, we are entering a new era of research into infectious disease.'

His colleague Johannes Krause added: 'Using the same methodology, it should now be possible to study the genomes of all sorts of historic pathogens.

'This will provide us with direct insights into the evolution of human pathogens and historical pandemics.'

The direct descendants of the same bubonic plague continue to exist today, killing some 2,000 people each year.

'We found that in 660 years of evolution as a human pathogen, there have been relatively few changes in the genome of the ancient organism, but those changes, however small, may or may not account for the noted increased virulence of the bug that ravaged Europe,' said Poinar.

'The next step is to determine why this was so deadly.'

Major technical advances in DNA recovery and sequencing have dramatically expanded the scope of genetic analysis of ancient specimens, opening new horizons in the understanding of emerging and re-emerging infections.

DeWitte, Bos and Schuenemann analyzed skeletal remains from victims buried in the East Smithfield 'plague pits' in London, located under what is now the Royal Mint.

Plague site: John Norden's famous map of London circa 1593

Psychedelic success: A cross-comparison of 10 genomes of 10 modern pathogen strains from the research team

Nice teeth: The secrets to the genome were derived from the dental pulp of plague victims

By targeting promising specimens - which had been pre-screened for the presence of Y. pestis - from dental remains of five bodies, the team was able to extract, purify and enrich the pathogen's DNA, filtering out background DNA such as human and fungal DNA.

Linking the 1349-1350 dates of the skeletal remains to the data allowed the researchers to calculate the age of the ancestor of the Yersinia pestis that caused the medieval plague.

This date coalesced sometime between the 12th and 13th centuries, indicating that earlier plagues such as the Justinian plague of the 6th Century - once thought to have been caused by the same pathogen - was likely caused by another, yet to be determined.

The Justinian plague spread across the Eastern Roman Empire, killing an estimated 100 million people worldwide.